The invention relates to a bookbinding machine with a transport system for continuously conveying stacks of sheets at cyclical intervals, consisting of a conveyer chain which runs around rerouting sprocket wheels and has individual links which engage movably in one another and have a multiplicity of clamps for clamping-in the stacks of sheets, which clamps are disposed at equal mutual intervals from one another and movably on the conveyer chain, driving-wise, and are guided in tracks on a machine frame; with a number of processing stations along rectilinear conveyer sections; with a jacket-laying-on device with a chain conveyer which is disposed underneath the plane of movement of the stacks of sheets, runs round rerouting sprocket wheels and has transporters which engage behind the jackets and feed them to the stacks of sheets in an aligned manner; and with an elevating platform which takes over the jackets and presses them onto the back of the stacks of sheets, moves synchronously with the clamps during the pressing-on of the jackets and optionally has pressing-on means for pressing the jackets onto the lateral regions of the stacks of sheets.
In the jacket-laying-on device, which is known from DE-OS 26 40 497, of a bookbinding machine, entrainment means which engage behind jackets are driven by a chain system which circulates at periodically changing speeds. In this process, the entrainment means feeding-in the jacket first move at a speed which is higher than the speed of circulation of the clamps, in order to catch up with a clamp which is running in front and to lay themselves on the latter for alignment purposes, and are then braked, against the action of a spring, while being laid on the clamp.
DE-OS 28 15 143 indicates another jacket-laying-on device in a bookbinding machine, in which the running speed of the chain for conveying the jackets is periodically increased and reduced by a differential gear unit and by a control cam provided with a curved groove, so that the location of the jacket in relation to the book block changes during the conveying of the said jacket, namely in such a way that the jacket advanced by the entrainment means overtakes the book block and the rear edge of the jacket and rear edge of the book block are thereby aligned in relation to one another.
The jacket-laying-on devices known from the prior art which have aligning systems are extremely costly from the design and production engineering points of view, as well as entailing considerable expenditure of time for setting up the aligning system.
The object of the invention consists in providing a jacket-laying-on device for bookbinding machines of the generic type, which requires a lower outlay on construction and guarantees high accuracy of positioning of the jacket in relation to the book block, with a high cyclical sequence. The jacket-laying-on device is also to be capable of being set up in an extremely short time and, in addition, of being adjusted, while the machine is running, with respect to different projections of the jacket in relation to the stacks of sheets.
The object is achieved by means of a chain conveyer or like conveyer means which is disposed in front of the elevating platform for the purpose of directly feeding-in the jackets in a cyclically synchronous manner in relation to the stacks of sheets and has projecting transporters which reach beyond rerouting sprocket wheels on the discharge side of the chain conveyer as far as a defined distance from the elevating platform, and the movement of which is controlled in such a way that they maintain their perpendicular position in the rerouting system after the feeding-in of the jackets. In a preferred development of the invention, the chain conveyer can be driven, with the transporters, by the driven sprocket wheel of the transport system and the jackets can be fed, with a defined projection in relation to the stack of sheets, to the elevating platform via the transporters in a continuous movement.
Other advantageous features of the invention form the subject of the remaining dependent claims.
With the aid of the jacket-laying-on device according to the invention, the jackets are fed directly to the elevating platform for pressing onto the back of the stack of sheets. The transporters take over the jackets detached by the laying-on system and transport them to the elevating element in a uniform pattern of movement. Accelerating and braking systems are not needed. As a result of the rerouting operation, the speed of transport of the transporters is automatically retarded, compared with the movement of the clamps, immediately after transfer to the elevating platform. Because of the transporters which project a long way, the chain conveyer can remain outside the range of movement of the elevating platform as well as of the pressing-on means for the lateral regions of the stacks of sheets. The direct driving of the chain conveyer by the driven sprocket wheel of the transport system of the bookbinding machine guarantees high accuracy of synchronism between the clamps and transporters.